Characterization of Two Forms of the 72,000 MW EBNA and a Cross-Reacting Cellular Protein

Abstract

Human cells transformed by Epstein-Barr virus (EBV) express virally determined nuclear antigens designated EBNA. The major component of EBNA, identified by immunoblotting, is a polypeptide with a variable molecular weight ranging from 72,000 to 89,000 daltons depending on the resident EBV genome (Strnad et al. 1981, Spelsberg et al. 1982, Luka et al. 1983). Kieff and co-workers (Heller et al. 1982, Hennessy and Kieff, 1983, Hennessy et al. 1983), showed that the 72K EBNA was encoded from a region on EBV DNA which contained the IR3 repeat sequence. This region encodes for a glycine-alanine polymer. The correct reading frame for translation of this EBV gene is known from the nucleotide sequence of a fusion gene between IR3 and Lacz, since the fusion gene encodes for a protein with epitopes for EBNA (Hennessy and Kieff 1983). Human and mouse cell DNA have interspersed repeat elements related to this EBV triplet, but it is not known, if the cellular sequences encode protein.